Numerous processes are currently utilized to apply images to substrates, such as by using masks, etching, photocopying, dye sublimation, dye diffusion thermal transfer, and ink jet, laser, and other printing techniques. The processes are less varied, however, when attempting to apply images to particle-filled resin materials, such as cultured marble. Such composite substrates have become very popular for a variety of home uses, in particular for kitchen and bathroom surfaces, because of their strength, durability, resistance to staining, and ease of cleaning.
It has been difficult to apply images deeply and permanently in resin materials. Consequently, image fading from wear or exposure to sunlight has been a major problem. Masking and etching have sometimes been used, but the processes have been expensive and time consuming.
For the most part, the industry has focused on applying images to substrates from a transfer medium, with the images formed from dyes capable of sublimation. In some cases, a substrate of resin material is formed and cured before applying the transfer medium. A gel coating may first be applied to a substrate, and the gel coat may also be allowed to cure. Then the transfer medium having an image formed by sublimable ink is brought into contact with the substrate or coating, and heat and/or pressure are applied to cause the image to sublimate into the substrate or the gel coat. Commonly, a heat press is used to apply substantial heat and pressure to facilitate the image transfer.
U.S. Pat. No. 7,001,660 (Garitano) discloses an image transfer method using a cured polymeric composite substrate. The substrate is brought into contact with an image transfer medium that carries an image formed by sublimable ink, while applying heat and/or pressure. U.S. Pat. No. 7,108,890 (Home) discloses applying a polymeric coating to a porous natural or synthetic surface. After the coating has cured, an image of sublimation inks is transferred to the coating from a transfer medium, by sublimation facilitated by heat and pressure. U.S. Patent Application Publication No. 2005/0227006 (Segall) discloses applying a gel coat to a substrate of composite material and then transferring an image to the coated composite by sublimation using heat and pressure.
FIG. 1 shows an example of a prior art image transfer process 10 involving polymeric substrate and images transferred to substrates or coatings by sublimation through heat and pressure. An image 12 is acquired from various means, such as a photograph or painting, and may be scanned by a scanner 14 into a computer 15 for editing. The computer 15 then prints the image on a transfer sheet 20 with a printer 16 employing dye sublimation inks.
Substrate 23 may be a natural product like stone, masonry, a ceramic, marble, or concrete, or a synthetic product, such as cultured marble or another polymeric composite material. If substrate 23 is a polymeric composite material, it is produced in a separate molding process (not shown). A liquid resin 26, such as a polyol resin, may be applied to the substrate 23 by any conventional technique, such as by brush 28 or spray 30. The resulting coating, referred to as a “receptor coating 24,” is allowed to cure by drying, hardening, absorbing, or reacting with a catalyst.
Next, transfer sheet 20 is applied to a surface of receptor coating 24, and is subjected to heat and pressure by a heat press 22. The heat and pressure cause the ink to sublime into receptor coating 24 over a sublimation period. The resulting coated substrate has an image 12 imprinted on receptor coating 24.
The entire image transfer process 10 may require several hours of time to cure substrate 23 and receptor coating 24. In addition, time is required to heat and press image 12 onto receptor coating 24 and then to cool substrate 23 and receptor coating 24. Furthermore, a large and expensive heat press 22 must be used to apply substantial heat and pressure, typically around 300-500° F. and 20-60 psi. The image transfer process 10 is also labor intensive, requiring a skilled craftsman to operate heat press 22 and another craftsman to mix and pour liquid resin 26 to form substrate 23 and receptor coating 24. Finally, unless receptor coating 24 has incorporated therein an ultraviolet (UV) radiation-resistant material, the resultant image 12 will exhibit poor light-fastness.
FIG. 2 shows a cross-section of a product 29 resulting from image transfer process 10 of FIG. 1. Substrate 23 has a receptor coating 24 with an image 12. Product 29 may be a polymeric product, such as a cultured marble surface in a kitchen or bathroom, a decorative stone, a cement or brick surface or wall, a pot or a ceramic container, or tiles in the entryway of a home.
This type of image transfer process 10 tends to be expensive and time consuming. Substantial cure time is required to cure liquid resin 26 of substrate 23 and of receptor coating 24 before applying image 12. Typically, a large and expensive heat press 22 is used to apply heat and pressure for the image transfer. Even then, the manufactured article exhibits poor light-fastness, particularly under prolonged exposure to the ultraviolet rays of sunlight, unless a separate UV-protective coating is applied.
This light-fastness weakness is tied directly to the use of dye sublimation inks. As is well known by those familiar with the art of inkjet printing, dyes inherently exhibit poor light-fastness due to the fact that each dye molecule functions to provide color and is therefore exposed to UV radiation. However, dyes must be used for sublimable inks since the particulate property of pigments cannot be maintained during sublimation. Accordingly, this weakness makes dye sublimation inks particularly unsuitable for applications involving cultured marble and some other resin composites, since the areas in which these materials are used are often exposed to direct sunlight. Therefore, the use of dye sublimation inks requires the application of an additional material to provide UV protection or resistance, which adds time and cost to the production process and reduces the flexibility of the application.
Moreover, the sublimation process is problematic due to the limitations of the dyes and dye colors and the necessity of special transfer materials having dye-acceptable coatings thereon, which add to the total cost of the process. In addition, since heat and pressure are required to drive the sublimation process, the necessity of using heat-resistant substrates has eliminated the use of some otherwise desirable materials. For example, the heat required for sublimation typically exceeds the heat distortion temperature limits of some composite materials, such as cultured marble.
In view of the foregoing, it will be appreciated that providing methods for transfer of an image to a resin material without the need for applying heat and/or pressure would be a significant advancement in the art.